1. Technical Field
The present invention relates to a cooling device of an onboard secondary battery.
2. Related Art
In recent years, there is known an electric vehicle (EV) and a hybrid electric vehicle (HEV) including a driving motor that outputs driving force of a vehicle and a secondary battery that supplies electricity to the driving motor. A secondary battery provided in such a vehicle is characterized in that the secondary battery tends to degrade as its battery temperature increases. Thus, in order to prevent the secondary battery from degradation, a technology for cooling the secondary battery is proposed.
For example, in Japanese Unexamined Patent Application Publication (JP-A) No. 2007-314139, a technology is disclosed which takes vehicle compartment air cooled by a cooling mechanism or the like into a space where a secondary battery is disposed, in order to cool the secondary battery.
Here, in the entire life of a vehicle, a parking time is far longer than a traveling time, and therefore the influence of a battery temperature in the parking time on degradation of a secondary battery is larger than the influence of a battery temperature in the traveling time of the vehicle. Thus, it is expected that the degradation of the secondary battery be reduced by reducing a temperature rise of the secondary battery at the time of parking. However, in the technology relevant to cooling of the onboard secondary battery of the past, it is sometimes difficult to reduce the degradation of the secondary battery at the time of parking.
In general, the vehicle compartment air is cooled by a cooling mechanism or the like, while driving the vehicle, in order to improve comfort of a driver. Thus, the cooling mechanism stops while the vehicle is parked, and therefore the temperature in the vehicle compartment can be high under direct sunlight in summer season. Thus, for example, in the technology disclosed in JP-A No. 2007-314139, the temperature of the vehicle compartment air can be high, and therefore it is sometimes difficult to cool the secondary battery, even if the vehicle compartment air is taken into the space where the secondary battery is disposed, while the vehicle is parked.